[RFC PATCH 12/56] x86/bugs: Reset SRBDS mitigations

David Kaplan
2025-10-13T14:35:29Z

Add function to reset SRBDS mitigations back to their boot-time defaults.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
arch/x86/kernel/cpu/bugs.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9139c8187913..9a9d5309aa56 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -993,6 +993,17 @@ static void __init srbds_apply_mitigation(void)
update_srbds_msr();
}

+#ifdef CONFIG_DYNAMIC_MITIGATIONS
+static void srbds_reset_mitigation(void)
+{
+ /* To cause the MSR bit to be cleared */
+ srbds_mitigation = SRBDS_MITIGATION_FULL;
+ update_srbds_msr();
+ srbds_mitigation = IS_ENABLED(CONFIG_MITIGATION_SRBDS) ?
+ SRBDS_MITIGATION_AUTO : SRBDS_MITIGATION_OFF;
+}
+#endif
+
static int __init srbds_parse_cmdline(char *str)
{
if (!str)
@@ -3913,5 +3924,6 @@ void arch_cpu_reset_mitigations(void)
l1tf_reset_mitigation();
mds_reset_mitigation();
mmio_reset_mitigation();
+ srbds_reset_mitigation();
}
#endif
--
2.34.1